Surgical operations or radiotherapy are being performed increasingly with the aid of so-called navigation or tracking systems. Patient data is determined using an imaging technique, for example, a computer tomography or magnetic nuclear resonance tomography, which can be used to indicate to the treating surgeon by means of a display output where his treatment tool is momentarily located. For example the position of the tip of an instrument within a part of the body to be treated can be displayed in order to be able to precisely operate at the places to be treated.
To enable such a navigation system to function, the momentary location of the patient or the part of the body to be treated needs to be known in situ during treatment. This updated positional data can then be assigned to the data received from the imaging process, for example, the data from a computer tomograph produced some time prior to treatment. After this assignment, the computer-assisted treatment may commence.